In windows comprising a movable sash having a locking system including one or more locking members cooperating with the window frame and a handle member operatively connected to said locking system, it is known to provide a mechanism for arresting the shaft in its locking position.
The arresting mechanism shall prevent an unintentional turning of the handle member away from the locking position and functions as a so-called children's safety device. Such safety devices are known in numerous embodiments, either as separate devices additional to the normal operating means of the window, or as integral parts thereof. When the operating means comprise a rotatable handle carried by the sash or the frame of the window and arranged to activate the locking members thereof, this handle may be associated with a key operated lock that has to be released in order to allow the handle to be turned away from the closing or locking position. When utilized in the intended manner, the lock provides an absolute guarantee against an unintentional opening of the window but, of course, only on the condition that the lock is operated by means of the key upon re-closure of the window. Similarly, the separate safety devices require an extra manual operation in order to serve their purpose.